(1) Field of the Invention
The present invention relates to the exercise of control over the flow of solid material within a pressurized enclosure and particularly to the actuation of a tubular spout which guides the flow of charge material being deposited on the hearth of a furnace. More specifically, this invention is directed to apparatus for controlling the position, with respect to a pair of transverse axes, of a steerable spout and especially a charge distribution spout supported within the throat region of a shaft furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the delivery of granular charge material to the hearth of a blast furnace. It is well known that the "profile" of the material deposited on the furnace hearth is a factor which influences production, particularly in modern furnaces which operate with a high internal pressure. Thus, in recent years considerable attention has been directed to exercising control over the disposition of the furnace charge material, which is delivered from above the furnace and thus flows under the influence of gravity, on the furnace hearth. Presently available devices for exercising control over furnace charge profile include a flow direction control member positioned within the furnace and controlled from the outside of the furnace. These control members receive vertically falling charge material and divert this material in a direction which will produce the desired pattern on the furnace hearth.
At present, charge distribution control mechanisms of the type generally described above are exemplified by the apparatus disclosed in U.S. Pat. No. 3,693,812. Such apparatus, which are rapidly replacing the previously conventionally employed "movable bell" type charging installations, are characterized by a rotatable and angularly adjustable charge distribution chute. These chutes are customarily suspended from the base of a rotary "ferrule" through which the charge material vertically falls. A suitable device is provided for the purpose of varying the angle of inclination of the chute about its point of suspension and independently of its rotation with the ferrule. A characteristic of these "bell-less top" charging installations is that an open chute, typically of semi-cylindrical shape, is utilized for aiming the direction of flow of the charge material and this chute always presents the same surface to the downwardly sliding granular material. Open chutes of the type exemplified by aforementioned U.S. Pat. No. 3,693,812, because of the nature of the directional control exercised thereover, are particularly well suited for movement so as to cause the deposited material to define a spiral or a series of concentric circles. The foregoing is true because the angle of inclination of the open chute can only be varied from the vertical upwardly to an angle which will cause the falling charge material to be deposited adjacent the periphery of the furnace hearth. The two different control actions, i.e., the rotation and inclination angle variation, are relatively easy to coordinate in these prior art installations. Further examples of prior art "bell-less top" charging installations, and control mechanisms for use therein, may be seen from U.S. Pat. Nos. 3,814,403; 3,864,984; 3,880,302; 3,929,240; and 4,071,166.
It has also been proposed to control the direction of flow of charge material falling toward a furnace hearth with a tubular distribution spout which undergoes oscillatory movement. Such oscillatory spouts would be suspended between a pair of mutually perpendicular suspension shafts of the type frequently referred to as a "Cardan suspension". With this type of suspension, the spout could pivot about each suspension shaft and, in order to insure that the charge material distribution achieved with the spout corresponded to the entire charging surface, the spout would have to pass through the vertical position as its angle of inclination was varied. This type of movement, of course, dictates that the charge distribution spout be tubular whereby its entire internal surface is exposed to the moving charge material. Such oscillatory spout type charging installations are disclosed in German patent application No. 2,104,116 and U.S. Pat. No. 4,243,351.
The control mechansims previously proposed for exercising control over the movements of oscillating charge distribution spouts of the type described above would be principally suitable for imparting movement which would cause the discharge end of the spout to undergo a rectangular or serpentine movement. Accordingly, although oscillating spouts offer certain advantages in comparison to the steerable open distribution chutes presently in use, the difficulty in coordinating the two pivotal motions so as to cause the discharge end of the spout to transcribe the desired path, particularly concentric circles or a spiral, has to date resulted in oscillating spout charge distribution systems remaining in the planning state.
To further briefly discuss the theoretical advantages of an oscillatory charge distribution spout when compared to a rotary and angularly adjustable charge distribution chute, oscillating spouts and their associated suspension and control mechanisms offer the potential advantage of ease of dismantling and removal from a furnace for repair. These advantages are described in aforementioned U.S. Pat. No. 4,243,351 another potential advantage resides in the fact that the entire internal surface of the oscillatory spout is exposed to the friction and errosive effects of the charge material and, accordingly, the wear of the spout is more uniform and distributed over a larger area. Thus, the rotary spout can be expected to have a longer service life when compared to the open chute wherein the same surface area is always exposed to the effects of the moving charge material.
Nevertheless, charging installations which employ a rotatable and angularly adjustable open chute have been in use for approximately ten years and have earned the confidence of users. Further, these uses benefit from years of experimentation and improvement of the equipment. These facts, coupled with the previous inability to simply and efficiently exercise control over an oscillatory spout located within a pressurized furnace, from the exterior of the furnace, so as to cause the discharge end of the spout to transcribe concentric circles or a spiral trajectory, these being the charge distribution patterns presently considered to produce optimum furnace operation, have precluded the adoption and use of the rotary spout type charging installation.